1. Field of the Invention
The present invention relates to a gas injector, and more particularly, to a gas injector adapted for an ALD process.
2. Description of the Related Art
Recently, with high integration of semiconductor devices, semiconductor devices have been downsized and thus vertical dimension thereof has been also downsized. Gate insulating layer and capacitor dielectric layer of dynamic random access memory (DRAM) are representative elements showing such the downsizing. In addition, in a semiconductor device whose design rule is 0.13 xcexcm or less, many attempts to substitute a new material for a conventional material have been made in order to meet requirements for new electrical properties. For example, instead of ONO dielectric layer as a capacitor dielectric layer, a multi-component high dielectric film such as BST or PZT has been widely researched.
To successfully form these new thin films at a very thin thickness of approximately 100 xc3x85, however, there is a need of a novel thin film forming method that is different from the conventional metal-organic chemical vapor deposition (MOCVD) method. For this need, atomic layer deposition (ALD) technology is widely used to form a thin film of the semiconductor device.
Unlike a typical chemical vapor deposition (CVD) method for depositing a thin film by simultaneously supplying component materials of the thin film, the ALD method is a technique for depositing a thin film in a unit of an atomic layer by repeatedly supplying the component materials on a substrate in turns. According to the ALD method, the thin film can be formed only by a chemical reaction of a surface of the substrate. Therefore, regardless of unevenness of the surface of the substrate, it is possible to form a thin film having a uniform thickness. Further, since a deposition thickness of the thin film is proportional not to a deposition time but to a material supplying period, it is also possible to precisely adjust the thickness of the thin film.
FIG. 1 is a schematic view of a conventional ALD apparatus. Referring to FIG. 1, a gas injector 20 is mounted on a reaction chamber 10 and various kinds of gases are supplied through a plurality of gas supply pipes 30 to the gas injector 20. A plurality of bombes (not shown) are mounted on the gas cabinet 70 and the gas supply pipes 30 are independently coupled with respective gas bombes.
Supply valves 30b provided with typical valves are mounted on a predetermined portion of the gas supply pipes 30 near the bombes. ALD valves 30a that are designed to be adaptable to the ALD process and capable of being closed/opened at a high speed are mounted near the gas injector. By-pass pipes 40 are mounted on gas supply pipes 70 that are mounted between the supply valves 30b and the ALD valves 30a. Also, ALD valves 40 are mounted on the by-pass pipes 40. An ALD PLC 50 and an ordinary PLC 60 control the ALD valves 30a and 40a and the supply valves 30b, respectively.
In case of the ALD process, a thickness of the thin film deposited at each cycle must be 0.1 xc3x85 to 1 xc3x85. Therefore, to form a thin film of 500 xc3x85 thick, a gas supply cycle must be 500 times to 5,000 times. Accordingly, if a thin film of approximately 500 xc3x85 is to be deposited on 100 wafers using the ALD process, the gas supply cycle must be 50,000 times to 500,000 times. This means that the ALD valves 30a mounted on the gas supply pipes must be turned on/off as often as 50,000 times to 500,000 times. In that case, however, a lifetime of a typical ALD value is terminated. Therefore, even when 100 wafers are used, it is necessary to repair the ALD apparatus, including a replacement of the ALD valves. Due to the frequent equipment repair, the yield as well as the reliability of the semiconductor device may be degraded. Further, there is a disadvantage that the expensive ALD PLC 50 should be used.
Therefore, the present invention has been devised to solve the above problems, and it is an object of the present invention to provide a gas injector, which is adapted for an ALD process without using any ALD valve.
To achieve the aforementioned object of the present invention, there is provided a gas injector. The injector includes: a body mounted on a reaction chamber in a vertically extending cylinder shape, and having a plurality of gas injection tubes penetrating bottom face thereof and a central tube penetrating each center of the bottom and top faces of the body; a motor having a rotary shaft inserted into the central tube; and a circular-plate shaped chopper connected to an end of the rotary shaft and having a predetermined cut portion, the chopper being magnetically sealed with the bottom face of the body by the rotation of the rotary shaft and rotating in a sealed state.